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Re: Work-Energy or Work-Kinetic Energy??



The issues of couples is interesting in this discussion. If you give the
conditions for the primitive (pristine :-) ) W-E thm to be Net Work done on
a point-like particle, couples are ruled out, because you can only have a
couple on an object that has extent.

OTOH If we compute the net work by summing the work done by the individual
forces of the couple (rather than computing the net force (summing the
forces) and then computing work), one will find (I think) that since the
point of application of the forces forming the couple are displaced that
both forces in the couple do work and that total work will equal the change
in the kinetic energy of the object.
Joel
----------
From: Martha Takats
To: QuistO; RAUBERJ; phys-l
Subject: Re: Work-Energy or Work-Kinetic Energy??
Date: Friday, November 07, 1997 9:48AM

The simple (trivial?) work-kinetic energy theorem some of us are
referring to in this discussion is nothing more or less than a
restatement of Newton's 2nd Law. Perhaps we are at fault for not
specifying the limitations of the theorem (we are talking about
particles, or, if rigid bodies, referring only to translational KE).
We don't pretend that it contains new information, only that it may
in some applications be more convenient to use than F = ma. And we
don't include couples because they contribute nothing to the net
force.
--
Martha Takats
Department of Physics and Astronomy
Ursinus College
Collegeville, PA 19426
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From: Martha Takats <mtakats@acad.ursinus.edu>
To: phys-l@atlantis.uwf.edu
Subject: Re: Work-Energy or Work-Kinetic Energy??
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